A U.S. official told CNN that Ghul is a "longtime facilitator, operator" within al Qaeda, and a "significant player."

It is believed that Ghul was captured soon after his arrival in Iraq, the official said.

Earlier Friday, Pentagon sources announced that U.S. forces had captured a man described as a top lieutenant to a man connected to Ansar al-Islam, a Kurdish guerrilla group that U.S. officials say is linked to Osama bin Laden's terrorist network.

Ansar al-Islam is accused of attacking U.S. troops in northern Iraq.

The suspect, identified as Husam al Yemeni, was captured last week along with other suspects during a raid near Fallujah in central Iraq, sources told CNN.

He is said to be a key associate of Abu Musab Al-Zarqawi. Pentagon officials call the capture "significant" and say it suggests they may be getting closer to finding Zarqawi.

In his address to the United Nations on February 5, 2003, Secretary of State Colin Powell named Al-Zarqawi's presence in northern Iraq as evidence of a "sinister nexus between Iraq and the al Qaeda terrorist network."

Meanwhile, senior U.S. military officials said U.S.-led coalition forces are making progress in their hunt for Izzat Ibrahim al-Douri, the highest-level Saddam Hussein loyalist still on the run.

Senior coalition sources have said they believe Ibrahim is responsible for organizing resistance fighters in Baghdad, Fallujah, Ramadi, Samarra and Tikrit.

The guerrilla insurgency continued this week, with most activity in Baghdad and the "Sunni Triangle," the region north and west of the capital. The latter saw three attacks in a 24-hour period Wednesday and Thursday that killed nine people, including two U.S. soldiers.

Intelligence from Iraqis is helping coalition forces zero in on Ibrahim's possible location, a U.S. military source said.

Ibrahim, No. 6 on the U.S. list of the 55 most-wanted Iraqis, was vice chairman of Iraq's Revolutionary Command Council and held a number of other high-level posts in Saddam's government.

Coalition intelligence sources said they believe he has been using underground tunnels and safe houses.

Iraqi insurgents take on al Qaeda tactics

The commander of U.S. ground forces in Iraq had recently discussed his suspicion that insurgents in Iraq, whose tactics resemble those of al Qaeda, may be receiving financial support from the terror group, in the country said.

"I think it's probably not appropriate for me to talk about al Qaeda in the sense of a concrete, proven presence," Sanchez said. "We're seeing al Qaeda-like tactics. We believe that there's training that's been conducted for some of the terrorists."

Although the instruction is not happening in Iraq, he said, al Qaeda seems to be training "those elements that are operating in here. And we think that there's also financing that has been taking place."

Sanchez said insurgent attacks were not becoming more sophisticated.

"We're starting to see an influx of improvised explosives that are very crude," he said. "Clearly they are still a learning and adapting enemy force."

Chopper crash kills 2

Two pilots were killed in northern Iraq on Friday when their OH-58 Kiowa Warrior helicopter crashed, U.S. Central Command said.

The cause of the crash was not immediately known. A report from a nearby helicopter did not mention hostile activity.

The deaths bring the total of U.S. troops killed in the war to 504, 349 of those in hostile circumstances.

U.S. Central Command said Friday that soldiers have conducted 184 patrols and eight raids within the past 24 hours, capturing 31 people.

Other developments

• A two-person U.N. security advance team has arrived in Iraq before the United Nations makes an assessment about whether it's possible to hold direct elections in advance of the June 30 political handover to Iraqis. The coalition and the Iraqi Governing Council have drawn up a plan for caucus-style elections to be held by May 31. Grand Ayatollah Ali al-Sistani, the top Shiite cleric, wants direct elections.

• Charles Duelfer, 51, former deputy executive chairman of the U.N. Special Commission on Iraq, will become the CIA's special adviser in the hunt for weapons of mass destruction, CIA Director George Tenet said Friday. (Full story)